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Ignatavicius: Medical-Surgical Nursing, 7th Edition Chapter 13: Assessment and Care of Patients with Fluid and Electrolyte Imbalances Key Points - Print HOMEOSTASIS The body has many control mechanisms, called homeostatic mechanisms to prevent fluctuations in fluid and electrolytes. ANATOMY AND PHYSIOLOGY REVIEW: PHYSIOLOGIC INFLUENCES ON FLUID AND ELECTROLYTE BALANCE Body fluids are composed of water and particles dissolved or suspended in water. The solvent is the water portion of fluids. Solutes are the particles dissolved or suspended in the water. When solutes express an overall electrical charge they are known as electrolytes. Body function depends on keeping the correct balance of fluid and electrolytes within each body fluid space. Specific processes control normal fluid and electrolyte balance so the internal environment remains stable even when the external environment changes. These processes are filtration, diffusion, osmosis, and active transport. They determine how, when, and where fluids and particles move across cell membranes. FLUID BALANCE: BODY FLUIDS A person’s age, gender, and amount of fat affect the amount and distribution of body fluids. o An older adult has less total body water than a younger adult. o An obese person has less total water than a lean person of the same weight because fat cells contain almost no water. o Women of any age have less total body water than men of similar sizes and ages related to more body fat. Assessment is key in managing imbalances. o Assess patients who have a sudden change in cognition for fluid and electrolyte imbalances. o Assess skin turgor on the forehead or the sternum of older patients. o Use daily weights to determine fluid gains or losses. o Ask patients about the use of drugs such as diuretics, laxatives, salt substitutes, and antihypertensives that may alter fluid and electrolyte status. o Correctly interpret laboratory electrolyte values. o Assess any patient with a fluid or electrolyte imbalance for falls risk. o Monitor the cardiac and pulmonary status at least every hour when patients with dehydration are receiving IV fluid replacement therapy. o Assess the bowel sounds; heart rate, rhythm, and quality; and muscle strength to evaluate the patient’s responses to therapy for an electrolyte imbalance. Copyright © 2013, 2010, 2006, 2002 by Saunders, an imprint of Elsevier Inc. Key Points - Print 13-2 Use a gait belt when assisting a patient with muscle weakness to walk or transfer. Do not give oral fluids to an unconscious patient. Offer or ensure that oral care is performed at least every 4 hours for patients with dehydration. The minimum amount of urine output per day to excrete toxic waste products, called the obligatory urine output, is 400 to 600 mL. Other normal water loss occurs through the skin, the lungs, and the intestinal tract. HORMONAL REGULATION OF FLUID BALANCE The endocrine system helps to control fluid and electrolyte balance. o Three hormones that help control these critical balances are aldosterone, antidiuretic hormone, and natriuretic peptide. SIGNIFICANCE OF FLUID BALANCE The human body requires a balance of body fluids, electrolytes, and acids and bases for best function. The most important fluids to keep in balance are the blood volume (plasma volume) and the fluid inside the cells (intracellular fluid). The most critical fluid balance to prevent death is maintaining blood volume at a sufficient level for blood pressure to remain high enough to ensure adequate perfusion and oxygenation of all organs and tissues. Balance of both water and electrolytes is needed for this very vital function. Activated angiotensinogen is angiotensin I, which is relatively weak. It is then acted on by another enzyme known as angiotensin converting enzyme or ACE, which converts angiotensin I into its most active form, angiotensin II. Angiotensin II starts several different activities that all work to increase blood volume and blood pressure. DEHYDRATION All patients are at risk for some degree of fluid imbalance because many health problems can disrupt fluid intake or output. In dehydration, fluid intake is less than what is needed to meet the body’s fluid needs, resulting in a fluid volume deficit. o Management of dehydration aims to prevent injury, prevent further fluid losses, and increase fluid compartment volumes to normal ranges. o Main strategies include assuring patient safety, fluid replacement, and drug therapy. o Ensure access to adequate fluids for patients who are unable to talk or who have limited mobility. FLUID OVERLOAD Copyright © 2013, 2010, 2006, 2002 by Saunders, an imprint of Elsevier Inc. Key Points - Print 13-3 Fluid overload, also called overhydration, is an excess of body fluid. o Fluid overload may be either an actual excess of total body fluid or a relative fluid excess. o Interventions for patients with fluid overload ensure patient safety, restore normal fluid balance, provide supportive care until the imbalance is resolved, and prevent future fluid overload. o Use a pump or controller to deliver intravenous fluids to patients with fluid overload. ELECTROLYTE BALANCE AND IMBALANCES Electrolyte imbalances can occur in healthy people as a result of changes in fluid intake and output, which are usually mild and easily corrected. o Severe electrolyte imbalances are life threatening. o Electrolyte homeostasis balances the dietary intake of electrolytes with the renal excretion or reabsorption of electrolytes. SODIUM The ECF sodium level determines whether water is retained, excreted, or moved from one fluid space to another. Serum sodium balance is regulated by the kidney under the influences of aldosterone, antidiuretic hormone (ADH), and natriuretic peptide (NP). HYPONATREMIA Hyponatremia is a serum sodium level below 136 mEq/L. o Sodium imbalances often occur with fluid volume imbalances because the same hormones regulate both sodium and water balance. HYPERNATREMIA Hypernatremia is a serum sodium level over 145 mEq/L. o Drug and nutrition therapies decrease high serum sodium levels. o Interventions used when sodium levels become life threatening include hemodialysis and blood ultrafiltration. POTASSIUM Keeping the large difference in potassium concentration between the ICF and the extracellular fluid (ECF) is critical for excitable tissues to depolarize and generate action potentials. Other functions of potassium include regulating protein synthesis and regulating glucose use and storage. HYPOKALEMIA Copyright © 2013, 2010, 2006, 2002 by Saunders, an imprint of Elsevier Inc. Key Points - Print 13-4 Hypokalemia is a serum potassium level below 3.5 mEq/L which can be life threatening because every body system is affected. o Drug and nutrition therapies help restore normal serum potassium levels. o Assess the respiratory status of all patients with hypokalemia. o Follow facility policy for cardiac monitoring in presence of hypokalemia. o Do not give intravenous potassium at a rate greater than 20 mEq/hr. o Never give potassium supplements by the intramuscular, subcutaneous, or IV push routes. o Use a pump or controller when giving intravenous potassium-containing solutions. o Assess the IV site of a person receiving IV solutions containing potassium hourly and document its condition. o Immediately stop the infusion of potassium-containing solutions if infiltration is suspected. HYPERKALEMIA Hyperkalemia is a serum potassium level greater than 5.0 mEq/L. o Even slight increases above normal values can affect excitable tissues, especially the heart. o Assess all patients with hyperkalemia for cardiac dysrhythmias and ECG abnormalities, especially tall T waves, conduction delays, and heart block. CALCIUM This mineral is important for maintaining bone strength and density, activating enzymes, allowing skeletal and cardiac muscle contraction, controlling nerve impulse transmission, and allowing blood clotting. Calcium enters the body by dietary intake and absorption through the intestinal tract. HYPOCALCEMIA Hypocalcemia is a total serum calcium level below 9.0 mg/dL. o Because the normal blood level of calcium is so low, any change in calcium levels has major effects on function. o Use a lift sheet to move or reposition a patient with chronic hypocalcemia. HYPERCALCEMIA o Hypercalcemia is a total serum calcium level above 10.5 mg/dL. o Small increases have severe effects on all systems. o Interventions for hypercalcemia aim to reduce serum calcium levels through drug therapy, dialysis, rehydration, and cardiac monitoring. PHOSPHORUS Copyright © 2013, 2010, 2006, 2002 by Saunders, an imprint of Elsevier Inc. Key Points - Print 13-5 Phosphorus is needed for activating vitamins and enzymes, forming adenosine triphosphate (ATP) for energy supplies, and assisting in cell growth and metabolism. It also functions in acid-base balance and calcium homeostasis. HYPOPHOSPHATEMIA Hypophosphatemia is a serum phosphorus level below 3.0 mEq/L. o Body functions are not usually affected even with rapid, wide changes in serum phosphorus levels, but may be with chronic hypophosphatemia. o Drugs that promote phosphorous loss are discontinued and oral replacement along with a vitamin D supplement may correct moderate deficiency. HYPERPHOSPHATEMIA Hyperphosphatemia is a serum phosphorus level above 4.5 mEq/L. o Management of hyperphosphatemia entails the management of hypocalcemia since hypocalcemia results when serum phosphorus levels increase. MAGNESIUM Magnesium is critical for skeletal muscle contraction, carbohydrate metabolism, adenosine triphosphate (ATP) formation, vitamin activation, and cell growth. Extracellular magnesium regulates blood coagulation and skeletal muscle contractility. HYPOMAGNESEMIA Hypomagnesemia is a serum magnesium level below 1.2 mEq/L. o Avoid administering magnesium sulfate by the intramuscular route. o Since hypocalcemia often occurs with it, interventions also aim to restore normal serum calcium levels. o Avoid administering magnesium sulfate by the IM route. HYPERMAGNESEMIA Hypermagnesemia is a serum magnesium level above 2.1 mEq/L. o In severe hypermagnesemia, excitable membranes may not respond to any stimulus. o All oral and parenteral magnesium are discontinued. CHLORIDE Imbalances of chloride usually occur as a result of other electrolyte imbalances and are corrected by interventions for correcting other electrolyte or acid-base problems. PATIENT EDUCATION Copyright © 2013, 2010, 2006, 2002 by Saunders, an imprint of Elsevier Inc. Key Points - Print 13-6 Explain the purpose of fluid restriction to the patient and the family to ensure cooperation and prevent misunderstanding. Encourage all patients to maintain a fluid intake minimum of 3 liters per day unless another condition requires fluid restriction. Teach all people to increase fluid intake when exercising, in hot or dry environments, or during conditions that increase metabolism such as fever. Instruct patients who exercise heavily (athletes) to take scheduled fluid replacement breaks. Instruct patients at risk for fluid imbalance to weigh themselves on the same scale daily, close to the same time each day, and with about the same amount of clothing on each time, and to monitor these daily weights for changes or trends. Instruct caregivers of older adults who have cognitive impairments or mobility problems to schedule offerings of fluids at regular intervals throughout the day. Teach patients to determine electrolyte content of processed foods by reading labels. Determine the patient’s food preferences and dislikes when planning an electrolyte restricted diet. Teach patients who are prescribed to take diuretics to take the drugs as prescribed. Teach patients who are taking digoxin or diuretics to measure their pulse for rate, rhythm, and quality. Include the person who prepares the patient’s meals when teaching about dietary electrolyte restrictions. Copyright © 2013, 2010, 2006, 2002 by Saunders, an imprint of Elsevier Inc.